We introduce our observational study of the orbital motion and the intrinsic variability of the double-lined spectroscopic binary beta Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of beta Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of beta Cen and find a very eccentric orbit (e=0.81) and similar component masses with a mass ratio M1/M2=1.02. beta Cen forms a challenge for current evolution scenarios in close binaries and it is also a puzzle how a massive binary with such a large eccentricity could have formed in the first place. Both the primary and the secondary exhibit line-profile variations. A period analysis performed on the radial velocity variations of the primary after prewhitening the orbital motion leads to the detection of at least 3 pulsation frequencies while the star does not show any periodic photometric variability. Based on observations obtained with the ESO CAT/CES telescope and the Swiss Euler/CORALIE telescope, both situated at La Silla, Chile.